# This file is part of The Vu Toolkit.
#
# The Vu Toolkit is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 3.0 of the License, or (at your option) any later version.
#
# The Vu Toolkit is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with The Vu Toolkit; if not, write to the Free
# Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
# 02111-1307 USA.
#
# Copyright © Zak Fenton 2008
#

module Vu
	# An immutable abstract colour class
	class Colour
	end
	
	# A colour composed of red, green, blue and an optional alpha component
	class RGB < Colour
		attr_reader :r, :g, :b, :a
		
		def initialize (r,g,b,a=1.0)
			@r = r
			@g = g
			@b = b
			@a = a
		end
		
		# A copy of this colour, darker by a given fraction (alpha left as is)
		def darker (f)
			RGB.new(r-r*f, g-g*f, b-b*f, a)
		end
		
		# A copy of this colour, lighter by a given fraction (alpha left as is)
		def lighter (f)
			darker(-f)
		end
		
		# A copy of this colour, multiplied by another opacity
		def with_opacity (o)
			RGB.new(r,g,b,a*0)
		end
	end
end

